This invention relates to the photoelectric scanning or reading of documents and in particular to an optical mark reader which reads the presence or absence of a pencil or similar mark at various locations on a sheet of paper.
It is common in elementary examinations and even in some more advanced examinations to give multiple choice questions. These are questions where the student is required to select the most appropriate answer of a number offered in the paper. The marking of such papers can be tedious and lengthy since there may be a number of "scoring" selections and no single unique answer.
The task has been alleviated to some degree by prior art techniques and devices that provide automatic reading of answer sheets. The extent of these prior art devices is given by the following patents: U.S. Pat. No. 3,953,364 issued on Sept. 29, 1976 to Firehammer et al, U.S. Pat. No. 3,761,688 issued on Sept. 25, 1073 to Cassel, U.S. Pat. No. 3,315,377 issued on April 25, 1967 to Stillwell, and U.S. Pat. No. 4,217,487 issued on Aug. 12, 1980 to Kjeer.
The Firehammer et al patent discloses a device for reading an examination answer sheet in which certain areas have been darkened by a lead pencil. Photoelectric cells provide analog voltages having magnitudes in accordance with the opacity of the marks on the sheet. The information is digitized and forwarded to a computer for processing. However, the Firehammer et al device uses a motor and drive roller to move the examination sheet past a photoelectric pickup station to read it, thereby adding to cost and complexity and making it subject to mechanical wear.
The Cassel patent discloses a high-speed optical card reader in which all the holes are read simultaneously. The reader in this device includes an input hopper for storing cards to be read, the reading means, and a transport means. The transport means includes a picker blade which is mounted for reciprocating movement parallel to the table and is conventionally driven by a crank and by levers. Therefore, the Cassel invention has been found to be deficient in two ways. First, it requires moving parts to function. Second, the Cassel invention reads "holes" by giving a positive output for a column element that is illuminated in comparison to remainder column element of the rows which are darkened. The Optical Mark Reader has no moving parts in its sensing mechanism and distinguishes a column element in that it is darkened in comparison to the remainder column elements in the rows, which are illuminated.
The Stillwell et al device is directed to a computer for "scoring" the answer sheet of a student's examination paper which senses marks on the paper using photocells. This device also requires moving parts to function. The paper is read by moving it under the sensing heads of the reading machine.
Kjeer shows a document scanner for determining the light transmissivity of the document using phototransistors. Like other prior art devices, the Kjeer document scanner uses moving parts to function.
The Optical Mark Reader (OMR) resembles a number of prior art devices in the fact that it will automatically read the presence or absence of a mark located at various locations on a sheet of paper. However, this invention is completely solid-state, with no moving parts. This greatly reduces mechaincal wear and alignment problems which account for the majority of breakdowns of currently available OMRS.
None of the references disclose a rapid digital output light transmissivity reader having no moving parts. All known prior art devices are subject to the problem of frequent breakdowns due to mechanical wearing of parts and mis-alignment of moving carriages.
Additionally, the reliability and availability of the prior art devices are further limited to the mean time between failure of the individual photocells in the sensing mechanism.
Finally, the prior art devices each require a special computer to interface with in order to convert the "raw" data into useable information.
In view of the foregoing discussion, it is apparent that there currently exists the need for a device capable of reading the presence cr absence of a mark on a sheet of paper where such device has no moving parts in its sensing mechanism; the device has multiple sensing elements in each cell of its sensing mechanism so that when one element disfunctions, accurate readings are still taken; and such device has its own internal logic circuits for processing the "raw" data such that any computer (even a micro-computer) may be the host computer.
The present invention is directed towards satisfying that need.